Upon removing the glass bulb enclosure, I was a bit surprised to see that only two power LEDs were used in this Cree bulb. Typically, you would see many more lower wattage LEDs put together to achieve higher wattage ratings. The two power LEDs are wired in series. Each power LED likely consists of eight to ten LED dies inside as the forward voltage drop of these two LEDs is measured at around 70V in operation, with each dropping around 35V. There is also a reverse polarity protection diode integrated into each of these power LEDs.

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5 Responses to “Teardown of a 65W Cree LED bulb”

LED bulb designers have drunk the kool-aid for too long; they are now in happy-happy land, smugly confident of their superior design skills, light years better than mere consumers who obviously know nothing and should listen obediently to designers, The Lighting Experts. Happy-happy Philips and Cree are waddling down in the mudhole with all the cheapo brands. A consumer interest organization should organize a campaign to push back against this nonsense.

Despite what Mr. Wong seems to think, many-die aggregated LEDs have been the norm in modern LED bulb manufacturing for years. The “500 individual pieces of 5mm LEDs christmas tree” bulbs are a relic of the previous decade. Unfortunately integrated LEDs are invariably series-connected to facilitate powering them from the mains, which implies that any die developing a fault withing a string can render the whole string inoperative, unless it happens to fail short. And while better heat-sinking would always be welcome, realities of LED efficiency being what they are, no power LED will be run “thermally comfortably” out here in the real world anywhere in the foreseeable future. All of them will run too hot no matter what you do. So no surprises here really, unless one is still naive enough, in 2018, to think “LEDs in general have the potential to live for tens of thousands of hours” actually means “your LED lightbulb will also live that long”. By all means, we should try to lengthen LED bulb life as much as we can; but all this is hardly surprising…

Yeah, it’s “hardly surprising” to us, and many of us have had direct or indirect bad experiences with them. BUT. But the LED bulb propaganda that is displayed in super/hypermarkets are all rosy, rosy, rosy. Some of us are no longer naive, but that’s not the point. The point is that the unrealistic propaganda is still happily being sold to consumers.

They have shortened the fins to almost nothing. *cough* I should call the fins plastic protuberances instead. Kerry thinks the bulbs are overheating. The LED parts were still fine, apparently. He also repurposed 3 apparently working Philips LED boards, which I guess supports his case. So maybe it’s the power board overheating and perhaps failing in some way. This is somewhat different from cheap corncob bulbs, where often a string would go dark when the weakest LED die failed. LED thermal tech worked, so why the failures? Are the failures unavoidable?

So, in the case of Kerry’s batch of Philips bulbs, LED component technology worked just fine. Why did the bulbs shut down? Bad board trace? Fractured cap? Power IC? Sure, potting the LED board and the power board and enclosing the whole enchilada in plastic is a good design for a premium LED bulb brand. Philips embracing some Shenzhen sleaze, good going.

I should also say that a film of dust on the hot plastic surface of the bulb would hamper airflow. No different from a CPU fan gathering dust if one does not do maintenance every few months. It’s going to hurt your thermal performance. Let’s assume not all bulbs are lucky enough to live a life in an air-conditioned office.

Let’s not leave out Cree either. Hey, what’s an electrolytic capacitor doing in a circuit that’s inside a small plastic case that has poor thermal performance and no fins worth speaking of? How long did they think that cap would last, even if it’s 105degC rated? Kerry said one Philips bulb (7W) was doing 60degC. On the plastic surface I guess. Now, how hot is it in there on the other side, this 9W bulb? Did they think electrolytic caps are used like silicon chips? Boys and girls, did the designers ever learned about Arrhenius… or did they ignore Arrhenius?

Somebody in the US, find a starving lawyer and slap a class action lawsuit on these guys, for oh maybe… *pinky on lips* ten billion dollars!